The present invention relates to an arrangement for transferring a traveling web, preferably a paper web which is to be dried, from a first drying cylinder at a first porous support belt to a second drying cylinder at a second porous support belt between the two cylinders. Such an arrangement is used, for example, in paper manufacturing machines, particularly in the dry end. The arrangement is used for transferring the web of paper being produced from the support belt of one dryer group, which customarily comprises a plurality of heatable drying cylinders, to the support belt of a subsequent dryer group, which also comprises a plurality of heatable drying cylinders. The arrangement can, however, also be used within a so called twin wire dryer group for the repeated transfer of the web to be dried from the upper dryer wire to the lower dryer wire, and vice versa.
Known transfer arrangements for this type are described in the following publications: 1) Federal Republic of Germany Utility Model 89 06 273, which is equivalent to U.S. Pat. No. 5,050,317; 2) Federal Republic of Germany Utility Model 90 01 209, which is equivalent to U.S. application Ser. No. 07/467,788; 3) U.S. Pat. No. 3,868,780 at FIG. 8; 4) U.S. Pat. No. 3,250,019; and 5) U.S. Pat. No. 5,101,577.
In accordance with Reference 1) or 2) the second guide roll along the path between the two cylinders lies within the loop of the first endless support belt and is developed as a suction roll or a vacuum roll and is also known as a "pick-up roll". As is known, the shell of the guide roll is perforated and a vacuum must be produced within the roll, preferably by means of a stationary suction box which defines a specific partially circumferential or angular suction zone. Suction rolls of this kind have high manufacturing costs and operating expenses. Therefore the arrangements according to References 3, 4 and 5 attempt to get along using ordinary guide rolls, i.e. rolls which are free of suction means. However, arrangements using ordinary guide rolls at the transfer between dryer groups do not always operate dependably, particularly at extremely high operating speeds now desired, which may be between 500 and 2000 m/min.
A certain improvement can be obtained according to FIG. 9 of Reference 5 because the travel paths of the two support belts form a small angle of divergence with each other upon departure from the second guide roll. This differs from the parallel guidance in References 3 and 4. However, diverging belt paths present a problem too. On one hand, the place at which the first support belt travels onto the first guide roll should be located at a sufficiently large distance from the web which is traveling together with the second support belt. This should avoid the web being lifted off again from the second support belt within this region by the rotation of the first guide roll, which causes a vacuum. This danger is present if the angle of divergence is selected to be too small or even if it assumes a value of 0, i.e. parallel guidance. On the other hand, it is not desired to make the angle of divergence too great, in order that the web may experience the smallest possible deflection at its place of transfer.